1. Field of the Invention
The invention relates in general to a ride control system for construction equipment, and more particularly, to a ride system which minimizes undesirable back and forth movement of construction equipment (i.e., a loader) due to the inertia of a load.
2. Background Art
One problem that has been observed while operating construction equipment having a load carrier (i.e. a bucket) is that the weight of a loaded raised bucket causes the entire loader (or other construction equipment) to bounce back and forth as it is driven. This is due primarily to the large moment of inertia of the load and of the loader across a comparatively short wheelbase.
Certain systems have been developed to counteract this tendency to bounce back and forth. Such systems include an accumulator which is selectively connected to the bucket hydraulics (the hydraulic cylinders of the boom) to essentially utilize these hydraulic cylinders as a suspension system. By cushioning and absorbing energy from the movement of the load, the ride becomes substantially less bouncy. Such systems are generally activated by the operator in the cab when a softer ride is needed.
While these systems have proven to be advantageous, such systems nevertheless suffer certain drawbacks. For example, in certain situations, the hydraulic pressure becomes unequalized between the accumulator and the hydraulic boom cylinders. In turn, if the accumulator pressure is substantially higher than that of the boom cylinders, as the user activates a conventional system the load within the loader may momentarily rise before the pressures reach equilibrium. Conversely, if the pressure in the boom cylinders is greater than that of the accumulator, then the load within the bucket may momentarily fall before the pressures reach equilibrium.
Accordingly, it is an object of the invention to provide a time delay between the activation of a soft ride system and the operation of the system, to, in turn, equalize the pressures between the accumulator and boom cylinder.
It is another object of the invention to provide a system which prevents bucket movement upon activation of a ride control system.
It is yet another object of the invention to provide a system which equalizes pressures between the accumulator and the boom cylinder prior to operation of a ride control system.
This and other objects of the invention will become apparent in light of the specification, drawings and claims attached hereto.
One aspect of the invention comprises a ride control system which includes a substantial equalizing means and a ride valve assembly. The means for substantially equalizing the pressure substantially equalizes the pressure within the head side of at least one boom cylinder with an accumulator. The ride valve assembly includes three positions, a first inactive position, a second active position and an intermediate equalizing position. The inactive position corresponds to one in which the ride valve assembly maintains isolation between the accumulator and at least one boom cylinder. The active position corresponds to one in which the ride valve assembly places the accumulator and at least one boom cylinder in communication with each other. The intermediate position corresponds to one in which the ride valve assembly maintains isolation between the accumulator and at least one boom cylinder and facilitates the activation of the substantial equalizing means.
In one embodiment of the invention, the substantial equalizing means comprises an equalizing valve having a first position wherein the accumulator is placed in fluid communication with a pump, a second position wherein the accumulator is placed in fluid communication with a hydraulic tank, and a neutral position wherein the accumulator is isolated from each of the pump and the hydraulic tank. The equalizing valve is selectively associated with each of the accumulator and at least one boom cylinder upon positioning of the ride valve assembly in an intermediate position. In such a position, a positive pressure difference between the accumulator and the at least one boom cylinder forces the equalizing valve into a second position. To the contrary, a negative pressure difference between the accumulator and the at least one boom cylinder forces the equalizing valve into a first position. Such movement continues until substantially equal pressures in each of the accumulator and the at least one boom cylinder force the equalizing valve into the neutral position.
In another preferred embodiment, the ride valve assembly comprises a starter valve and a follower valve. A rocker is associated with each of the starter valve and the follower valve. The rocker facilitates corresponding movement between the starter valve and the follower valve.
In one such embodiment, the starter valve is associated with each of the accumulator and the head side of the at least one boom cylinder. Additionally, the follower valve is associated with each of the rod side of the at least one boom cylinder, a hydraulic tank and the substantial equalizing means.
In another such embodiment, the ride control system further includes an axial port associated with the starter valve, the axial port having an orifice to control the maximum quantity of fluid passing to the starter valve, to, in turn, control the rate of movement of the starter valve from each of the inactive position to the active position. In one embodiment, the orifice comprises a helically wound path having a predetermined cross-sectional area. In another such embodiment, the axial port further includes a check valve. The check valve facilitates unidirectional flow of fluid from within the starter valve at a greater flow rate than the orifice.
In another aspect of the invention, the invention comprises a ride control system comprising an equalizing valve and a ride control valve. The equalizing valve includes a neutral position wherein the accumulator is isolated from a pump and from a hydraulic tank, a first position wherein the accumulator is in fluid communication with a pump and a second position wherein the accumulator is in fluid communication with the hydraulic tank. The equalizing valve further includes a first port associatable with the accumulator and a second port associatable with the head side of the at least one boom cylinder. The equalizing valve is urged into a first position wherein the pressure within the accumulator is less than that of the at least one boom cylinder and a second position wherein the pressure within the accumulator is greater than that of the at least one boom cylinder, and a neutral position wherein the pressure within the accumulator and the at least one boom cylinder are in substantial equilibrium. The ride control valve includes a first position wherein the accumulator is isolated from the at least one boom cylinder and a second position wherein the accumulator is in fluid communication with the at least one boom cylinder. The ride control valve further includes means for activating the equalizing prior to placement in the second position.
In one embodiment, the rod side of the at least one boom cylinder is placed in fluid communication with a hydraulic tank. In another embodiment, the system further including at least one switch associated with the ride control valve, the at least one switch capable of causing the ride control valve from a first position to a second position.
The invention further comprises a method for controlling the ride of a user. The method comprises the steps of: activating a ride control system, comparing the pressure within the accumulator and a head side of at least one boom cylinder, associating the accumulator with a pump if the pressure in the head side of the at least one boom cylinder is greater than that of the accumulator, associating the accumulator with a hydraulic tank if the pressure in the head side of the at least one boom cylinder is less than that of the accumulator, isolating the accumulator from either of the hydraulic tank or the pump when the pressure between the head side at least one boom cylinder is substantially equalized with that of the accumulator, and, placing the accumulator and the at least one boom cylinder in fluid communication.
In a preferred embodiment, method further comprises the step of placing the rod side of at least one boom cylinder in fluid communication with a hydraulic tank.
The invention further comprises another method of controlling the ride of a user comprising the steps of providing a switch for activating a ride control, providing a time delay between the activation of the switch of the user and the activation of a ride control system, and, equalizing the pressure between the accumulator and a head side of at least one boom cylinder during the time delay.
In one embodiment, the time delay is less than 3 seconds.